A Bit More Detail

Assorted Personal Notations, Essays, and Other Jottings

Posts Tagged ‘tau ceti

[NEWS] Four science links, from water on the frontier to climate change to Tau Ceti exoplanets

  • At Wired, Matt Simon explores the remarkably wrong-headed theory of the 19th century US that “rain follows the plough.”
  • These National Geographic photos of the unexplored lakes in Angola that feed the Okavango are remarkable.
  • Rachel Brown examines billy burr, the Colorado hermit whose collection of decades of climate data is invaluable.
  • Universe Today notes a new study confirming the existence of Tau Ceti e and f, potentially habitable rocky exoplanets just 12 light years away.

Written by Randy McDonald

August 9, 2017 at 10:59 pm

[BLOG] Some Monday links

  • The Dragon’s Gaze links to a paper noting how Tau Ceti’s debris disk is not like our solar system’s.
  • Language Hat talks about writers who want anonymity.
  • Joe. My. God. notes the return of homophobic protesters in France.
  • The Map Room Blog shares hazard maps of various Yukon communities.
  • Marginal Revolution notes that India’s biometric smartcards works, and notes diversity does not reduce economic growth.
  • Peter Rukavina shares some late 1990s photos of cows taken with an early digital camera.
  • The Volokh Conspiracy notes the recent controversy over Ruth Bader Ginsburg.
  • Window on Eurasia argues Russia might invade Ukraine more openly before January but also suggests that Russia is quite brittle.

[BLOG] Some space science links

  • Centauri Dreams considers the prospects for habitable worlds at Tau Ceti considering the composition of planets and the star’s evolution over time, considers the need for consistent observation in SETI programs, looks at possibly detectably volcanic 55 Cancri e, wonders if Fermi bubbles are detectable, considers stellar drift in the context of expanding interstellar civilizations, and looks at exoplanets with circular orbits.
  • The Dragon’s Gaze notes that Kapteyn’s Star apparently does not support habitable-zone exoplanets, suggests that the superdense atmosphere of even a Venus analog could be eroded fairly quickly by a red dwarf, wonders if the G2 cloud at the galactic centre is a planetary embryo, wonders if water-rich asteroids have been detected impacting a white dwarf, and considers methane exoplanets.
  • The Dragon’s Tales wonders if the geysers of Enceladus feeds the E ring of Saturn, looks at thermal anomalies on Enceladus, imagines ways to detect Europa’s tides by space probe flybys, and compares the arroyos of Mars and Earth.
  • The Planetary Society Blog notes how radio astronomy can be contaminated by Earthly pollution, notes the society’s recent lightsail launch, and looks at Ceres.

[LINK] “The Chemical Composition of τ Ceti and Possible Effects on Terrestrial Planets”

The Dragon’s Gaze linked to an interesting speculative paper about the planets of Tau Ceti. A nearby solar analog known to have multiple planets, this star has a different elemental composition from our own sun. What consequences would this have for planets made from Tau Ceti’s primordial protoplanetary disk?

{\tau} Ceti (HD10700), a G8 dwarf with solar mass of 0.78, is a close (3.65 pc) sun-like star where 5 possibly terrestrial planet candidates (minimum masses of 2, 3.1, 3.5, 4.3, and 6.7 Earth masses) have recently been discovered. We report abundances of 23 elements using spectra from the MIKE spectrograph on Magellan. Using stellar models with the abundances determined here, we calculate the position of the classical habitable zone with time. At the current best fit age, 7.63 Gy, up to two planets (e and f) may be in the habitable zone, depending on atmospheric properties. The Mg/Si ratio of the star is found to be 1.78, which is much greater than for Earth (about 1.2). With a system that has such an excess of Mg to Si ratio it is possible that the mineralogical make-up of planets around {\tau} Ceti could be significantly different from that of Earth, with possible oversaturation of MgO, resulting in an increase in the content of olivine and ferropericlase compared with Earth. The increase in MgO would have a drastic impact on the rheology of the mantles of the planets around {\tau} Ceti.

Written by Randy McDonald

April 6, 2015 at 9:43 pm

[BLOG] Some Monday links

  • The Burgh Diaspora points to articles discussing Germany’s ongoing demographic issues.
  • Crooked Timber’s John Quiggin meditates on the rapid urbanization of China.
  • Daniel Drezner expects somewhat more out of the recent Iranian election of a moderate president than of North Korea’s latest diplomatic moves.
  • The Dragon’s Tales’ Will Baird shares the news that none of the planets discovered orbiting Tau Ceti are likely to be habitable, e being Venus-like and f closer to Mars. There’s still space for a low-mass planet orbiting between e and f, though, right?
  • Geocurrents criticizes the recently publicized linguistics thesis claiming that languages which have ejective consonants are likely to have evolved in mountainous areas, where these sharp sounds are suited to area with low air pressure.
  • Marginal Revolution’s Tyler Cowen agrees now with Dani Rodrik’s long-staning critique of Turkish politics this past decade as undemocratic.
  • The New APPS Blog notes the blemishing of Erdogan’s record in Turkey and mass protests in Brazil’s Sao Paulo over public transit.
  • The Power and the Money’s Noel Maurer wonders if the Colombian-American alliance might worsen Colombia’s insurgencies.
  • Peter Rukavina shares the GIS numbers of Prince Edward Island, the geographical coordinates of a box encompassing the island province.
  • Torontoist notes that Toronto saw the first pay-TV show, a 1961 Bob Newhart special.
  • The Volokh Conspiracy notes the imprisonment in Egypt of a Muslim cleric convicted of offending Christians.

[REVIEW] Michael McCollum, The Sails of Tau Ceti

There have been many mentions of past appearances of worlds of Tau Ceti in science fiction, but so far as I know, few have have brought up Arizona-based science fiction writer Michael McCollum‘s 1992 The Sails of Tau Ceti.

I read the book again wanting to really like it. McCollum was a very active hard SF writer in the 1980s and 1990s, at least from my young perspective as I bought interesting-looking new titles in used book stores on Prince Edward Island. His bibliography in his German Wikipedia article is extensive. (Curiously, the article has no English-language counterpart.)

(Spoilers follow!)

The ideas behind The Sails of Tau Ceti is certainly audacious. Centuries after the mysterious nova destroyed Tau Ceti that 25th of August, 2001, the inhabitants of our industrialized solar system detect a light sail craft apparently pushed into interstellar flight by the light of the nova. Starhopper, the first prototype starship, is repurposed to intercept the craft before it enters our solar system. Carrying, among others, the software engineer Tory Bronson, they rendezvous with the craft only to discover that it is a crewed vehicle, an O’Neill-type habitat housing tens of thousands of hexapodal Phelans fleeing the ruin of their home system and seeking succor in ours. Bronson is convinced to represent the refugees and their case to humanity.

This habitat is just the vanguard of tens of thousands of more habitats light-months behind, carrying with them a total of three billion Phelan refugees. If they’re refused settlement rights in Sol system, then they’ll leave reluctantly. Humans wouldn’t want them to leave, though. The Phelans had to flee Tau Ceti in the first place because a radical faction among them accidentally triggered their star’s nova. In order to avoid the stranding of the fleet deep in interstellar space and the extinction of their portion of the Phelan species, they will make Sol go nova. Can Troy Bronson bridge the gap between the two species and prevent this catastrophe?

A minor kibbitz. The Phelans are noted as sending ships not only to our solar system but to Epsilon Eridani, Epsilon Indi, and Alpha Centauri, in other words the three closest Sun-like stars to our own planetary system other than lost Tau Ceti. Looking at the Internet Stellar Database, the Phelans had other options: Omicron 2 Eridani, or 40 Eridani, is closer to Tau Ceti than Epsilon Indi (10.2 light years versus 11.5), while 82 Eridani is just two thousand astronomical units further from Tau Ceti than Sol (both roughly 11.9 light years from the Phelans’ home system). Especially if the pre-nova Phelans were aware of humanity through our radio pollution and uncertain about our attitudes towards alien refugees, in-universe wouldn’t the Phelans have explored other, potentially safer, options. (I’m guessing that the data on the location of Sun-like stars in the neighbourhood of Tau Ceti that’s a simple Google search in 2013 was more problematic 21 years ago.)

One review says that The Sails of Tau Ceti is “[n]ot exactly a usual first contact story, not exactly a usual alien refugee story, not exactly an alien invasion story.” This is true, I suppose, but I don’t think it’s as distinctive as all that. Desperate alien refugees demanding a place to live in our solar system is a trope that frequently appeared in science fiction before this novel’s publication. McCollum’s sketch of a solar system on the verge of starflight, industrialized and colonized but still dominated by a populous and habitable Earth, is plausible enough as a trope to have appeared elsewhere. The character of Tory Bronson does have a lot of potential. Leaving aside the entirely plausible profession of software engineer, trained to ensure that the different programs of a very complex long-range space mission work together without causing an abort-retry-fail scenario, and the drama inherent in her position as the only being who can prevent a catastrophe that would consume the lives of billions, the computer chip networked with her brain gives her unusual potential.

The problem is that this novel is not particularly anything. I may have been more credulous when the book came out, but re-reading the novel it didn’t seem credible that McCollum would go to great lengths to detail human and Phelan civilization and then not find a way to save both from annihilation. If there was a final, frankly understandable, breakdown of human-Phelan relations, then Tory Bronson and everyone and ever place she knew would have been destroyed without leaving any legacy, and the experience of reading the novel would have been pointless. Tory Bronson could also have been a compelling character, but even her two different love interests and the unusual mental capacities granted her by her computer implants were barely touched upon. She was a character not very distinguishable from others. (It might not be fair to criticize McCollum, writing in 1992, for not developing Bronson’s relatively rare computer implants into a more thoroughly transhumanist imagining of the future.) Even the Phelans, as physically distinctive as they were, seemed to be hexapodal humans, with only lip service lent to the ideas that the veneer of human culture adopted by the first Phelans to enter the solar system is just that, and that the Phelans are fundamentally not human.

To a considerable extent, The Sails of Tau Ceti felt like it was only the introduction to a much broader and potentially more interesting universe. In the novel’s final passage, with a preliminary human-Phelan accord behind her, Bronson imagined what the new human-Phelan civilization might accomplish, imagining the new bispecies civilization of Sol contacting the other Phelan colony systems. The Sails of Tau Ceti, alas, never had any sequels written in such a future. Maybe if there were, I would have been happier with the book.

Written by Randy McDonald

January 10, 2013 at 2:44 am

[LINK] The Tau Ceti system

A large part of me wants to making the posting of maps of planetary systems a daily feature. I’ll satisfy myself by reposting the below map, drawn up by the Planetary Habitability Laboratory at the University of Puerto Rico at Arecibo of the orbits of the five worlds discovered orbiting nearby Tau Ceti (Sol Station, Wikipedia), after Wednesday’s remarkable announcement. It turns out that a dense cloud of debris in-system might mean a planet would get heavily bombarded with cosmic detritus, but certainly doesn’t mean planets won’t form in the first place.

Chart of the Tau Ceti system

This came with this press release authored by Abel Mendez Torres, who made the point that Tau Ceti e (orbiting just inside the inner edge of the habitable zone, makred in blue) and Tau Ceti f (the outermost planet, orbiting just inside the outer edge of the habitable zone) are only marginally habitable.

Tau Ceti e doesn’t look very promising.

The planet Tau Ceti e orbits close to the inner edge of the habitable zone. It receives about 60% more light than Earth from the Sun making it a hot planet probably only habitable to simple thermophilic (heat-loving) life. Its mean global surface temperature should be near 70°C assuming a similar terrestrial atmosphere. However, it is likely that superterran planets have much denser and heat trapping atmospheres and Tau Ceti e might be instead dominated by a strong greenhouse effect making it more likely a super-Venus than a super-Earth. Without any knowledge of its atmosphere we are not able to tell if it is a mildly hot planet tolerable for simply life forms or a very hot non habitable Venus-like world. Tau Ceti e has an Earth Similarity Index of 0.77 assuming a more terrestrial-like atmosphere.

Tau Ceti f, now, might well be more promising.

The planet Tau Ceti f orbits close to the outer edge of the habitable zone. It only receives about 27% the light of Earth from the Sun making it a cold planet probably only habitable to simple psychrophilic (cold-loving) life. Its mean global surface temperature should be near -40°C assuming a similar terrestrial atmosphere. However, it is likely that as Tau Ceti e, it is also dominated by a strong greenhouse effect making it even acceptable for complex life, which requires temperatures from 0°C to 50°C. Without any knowledge of its atmosphere we are not able to tell if it is a frozen Mars-like planet tolerable for simply life forms or even an Earth-like world. Tau Ceti [f] has an Earth Similarity Index of 0.71 assuming a more terrestrial-like atmosphere.

It’s worth noting that there is a very large gap between e at ~0.55 AU and f at ~1.35 AU. Might there be other planets, smaller planets, squarely in Tau Ceti’s habitable zone? (0.7 AU seems to be the right distance.)

Written by Randy McDonald

December 21, 2012 at 9:21 pm